Method of controlling HF alkylation reaction temperature

ABSTRACT

A control system and method for regulating the reaction zone temperature in a process for the acid-catalyzed alkylation of an isoparaffin with an olefinic feed stream containing mixed olefins. The temperature is adjusted to obtain the optimum, for a given feed composition, in order to maximize the octane rating of the liquid alkylate product. The control system effects rapid compensation for changes in feed composition which, at a fixed reaction zone temperature, otherwise adversely affects the octane rating.

United States Patent Zabransky Dec. 30, 1975 METHOD OF CONTROLLING HF3,018,310 1/1962 Van Pool... 260/683.48 ALK L O REACTION TEMPERATURE3,200,883 8/l965 Phillips 260/683.48 3,463,6l3 8/1969 Fenske et al...1208/DIG. l Inventor: Robert ZabranSky, Oak Brook, 3,751,229 12/1973Bajek et al 208/DlG. 1

Ill.

[73] Assignee: Universal Oil Products Company, r m ry EXaminerDelbert E-Gant Des Plaines, lll. Assistant Examiner-G. J. Crasanakis Attorney,Agent, or Firm-James R. Hoatson, Jr.; [22] Flled' 1974 Robert W.Erickson; William H. Page ll [2l] Appl. No.: 528,389

Related U.S. Application Data [57] ABSTRACT [62] Division of 468,956,May 10, 1974- A control system and method for regulating the reactionzone temperature in a process for the acid- [52] 260/683'48; 208/DIG- 1;235/5113 catalyzed alkylation of an isoparaffin with an olefinic [51]Int. Cl. C07C 3/54 f d Stream containing mixed fi The tempera- [58]Field of Search..... 260/683.48, 683.62, 683.58, mm isladjusted to bt ithe optimum, for a given 260/683-43 208/DIG- 1 feed composition, inorder to maximize the octane rating of the liquid alkylate product. Thecontrol system [56] References C'ted effects rapid compensation forchanges in feed com- UNITED STATES PATENTS position which, at a fixedreaction zone temperature, 2,881,235 4 1959 Van Pool 260/683.48Otherwise adversely affects the Octane rating- 2,990,437 6 1961 13 260683.48 3,002,818 1011961 erger 6 Claims, 1 Drawing Figure Berger260/683.48

HF Stripper Daprapam'zer Can fro/la! Comparator METHOD OF CONTROLLINGI-IF ALKYLATION REACTION TEMPERATURE RELATED APPLICATION The presentapplication is a division of my copending application Ser. No. 468,956,filed May 10, 1974, all the teachings of which copending application areherein incorporated by specific reference thereto, and is being filed tocomply with a requirement for restriction.

; APPLICABILITY OF INVENTION The control system herein described isintended for utilization in a process for the production of a normallyliquid alkylate product via the reaction of an isoparaffin with anolefin. Although intended for use in any acid-catalyzed alkylationprocess e.g. sulfuric acid alkylation my invention is most applicable tothose processes which are effected in contact with a hydrogen fluoridecatalyst. For more than a quarter of a century, the demand forhigh-octane fuels, possessing enhanced anti-knock characteristics, hasincreased at a staggering rate. These improved fuels are required involuminous quantities to satisfy the ever-accelerating degree ofconsumption. Within the petroleum industry, various processes have beendeveloped which have proved successful in alleviating the intertwinedproblems attendant supply, quality and demand. Among the first of suchprocesses was the acid-catalyzed alkylation of an isoparaffin with anolefin, both generally normally vaporous, to produce a higher molecularweight, normally liquid isoparaffin. Since isoparaffins, in contrast tonormal paraffins, possess significantly higher octane ratings andblending values, and thus'improve antiknock properties, processescapable of efficiently effecting such a reaction have gained, andcontinue to gain wide acceptance within the petroleum industry.

For many economic and technical reasons, well known to those having therequisite skill in the appropriate art, that alkylation processcatalyzed by a hydrogen fluoride catalyst predominates. HF alkylation ofan isoparaffin with an olefin has, since the advent thereof, experienceda multitude of changes and improvements with respect to unit designand/or operating techniques. The control system encompassed by myinventive concept also constitutes an improvement which affordsenhancement of operational stability, while simultaneously providingeconomic advantages.

Although applicable to the alkylation of an olefinic hydrocarbon havingfrom about 3 to about 7 carbon atoms per molecule, with an isoparaffinhaving from about 4 to about 7 carbon atoms per molecule, the presentcontrol system is uniquely advantageous in those processes whereisobutane is alkylated with an olefinic feed stream containing at leasttwo olefins selected from the group consisting of propylene, 1- butene,Z-butene and isobutylene. Therefore, in the interest of brevity, furtherdescription of the control system and alkylation process will bedirected toward the HF-catalyzed alkylation of isobutane with mixedolefins having three or four carbon atoms per molecule. Many processeswhich are integrated into an overall petroleum refining operation resultin product streams containing significant quantities of the lowermolecular weight olefinic hydrocarbons. Principal among such processesis the well known fluid catalytic cracking process; other processesinclude thermal cracking, or

pyrolysis units, coking operations and visbreaking. The olefinic feedstreams from one or more of these processes are generally recovered byway of gas concentration facilities which are specifically intended toconcentrate the C and C -olefins. Exemplary of such mixed olefinconcentrates is one containing about 51.3% by volume propylene, 48.2% byvolume of mixed butylenes and about 0.5% by volume of mixed amylenes.

Investigations have indicated that the quality of the normally liquidalkylate product is, at a selected reaction zone pressure, dependentupon the temperature at which the reaction mixture is maintained withinthe reaction zone. Since the acid-catalyzed alkylation process isexothermic, temperature control of the reaction mixture, via indirectheat exchange with a suitable cooling medium, has been, and continues tobe a commonly-practiced technique. This relatively simple temperaturecontrol system will suffice where the feed stream is a substantiallypure olefinic hydrocarbon.

' However, the olefinic feed streams in virtually 100% of theacid-catalyzed alkylation processes constitute a mixture of two or moreof the aforementioned olefinic hydrocarbons. This contributes a degreeof complexity with respect to temperature control of the reactionmixture. Considering, for the sake of illustration, substantially pureolefinic feed streams, the quality of the alkylate produced froml-butene is improved by increasing the reaction temperature, while thatproduced from either 2-butene, or isobutylene is improved by decreasingthe temperature of the reaction mixture. Additionally, a higher qualityalkylate product is produced from a propylene feed stream at highertemperatures than those which are optimum for the alkylation of C-olefins. Since the character of the olefinic feed stream is dependentupon the operation of other units within the overall refinery, whichunits are subject to their own peculiar operating parameters, thecomposition of the olefinic feed stream introduced into the alkylationsystem is constantly changing.

The control system of the present invention affords a method foreffecting the rapid compensation of feed stream composition changes withrespect to the quality of the normally liquid product. There is affordedan enhancement of the steady-state operation of the system, particularlywith respect to the stability of alkylate product quality, as well asthe economic advantages attendant an increase in operational efficiency.

OBJECTS AND EMBODIMENTS A principal object of the present invention isto afford an improvement in the hydrogen fluoride-catalyzed alkylationof olefinic hydrocarbons. A corollary objective is to enhance thecharacter of steady-state operation attendant the alkylation of anormally vaporous isoparaffin with a normally vaporous olefinichydrocarbon to produce a normally liquid alkylation product.

Aspecific object of my invention involves the control of reaction zonetemperature when alkylating an isoparaffin with a mixed olefinic feedstream.

Therefore, one embodiment of my invention provides a control system foruse in a process for alkylating an isoparaffin with an olefinic feedstream, to produce a normally liquid alkylate product, in which processsaid feed stream (1) contains at least two olefinic hydrocarbons and,(2) is contacted in admixture with a hydrogen fluoride catalyst, in areaction vessel, which control system regulates the temperature withinsaid reaction vessel and comprises, in cooperative combination: (a)conduit means for introducing a cooling medium into said reactionvessel, and for removing it therefrom, said cooling medium indirectlycontacting the reaction mixture within said vessel; (b) flow-varyingmeans for adjusting the flow of said cooling medium into said reactionvessel; (c) a hydrocarbon analyzer receiving a sample of said normallyliquid alkylate product and developing an output signal representativeof a composition characteristic of said sample; and, (d)signal-receiving means 'to which said output signal is transmitted, saidsignal-receiving means in turn transmitting said signal to saidflow-varying means, whereby the flow of said cooling medium is adjustedin response to said composition characteristic.

In another embodiment, my inventive concept encompasses a process foralkylating an isoparaffin with an oleflnic feed stream, containing atleast two olefins, which process comprises the steps of: (a) reactingsaid isoparaffin with said feed stream, in admixture with a hydrogenfluoride catalyst, in an alkylation reaction zone, at alkylatingconditions resulting in a reaction product effluent containing normallyliquid alkylate; (b) regulating the temperature of the reaction mixture,within said reaction zone, through indirect contact therein with acooling medium, the flow of which is adjusted by flow-varying means; (c)recovering said normally liquid alkylate from said product effluent; (d)introducing a sample of said alkylate into a hydrocarbon analyzer anddeveloping therein an output signal which is representative of acomposition characteristic of said sample; and, (e) transmitting saidoutput signal to signal-receiving means and from said signal-receivingmeans to said flow-varying means, whereby the flow of cooling medium andthe temperature within said reaction zone is adjusted in response tosaid composition characteristic.

Other objects and embodiments will become apparent from the followingadditional description of the present inventive concept and the controlsystem encompassed thereby, as well as from the description of theaccompanying drawing. In one such other embodiment, the output signal istransmitted to comparator means which compares the rate of change andactual value of the composition characteristic, generates a secondoutput signal and transmits said second signal to said signal-receivingmeans.

PRIOR ART Candor compels recognition and acknowledgement of the factthat the prior art is replete with a wide variety of publications,inclusive of issued patents, directed toward the acid-catalyzedalkylation of an isoparaffin with an olefin. This is particularly truewith respect to hydrogen fluoride alkylation which traces itsdevelopment over an approximate 30-year period. Any attempt herein toexhaustively delineate the hydrogen fluoride alkylation art wouldconstitute an exercise in futility. However, it is believed that a briefdescription of several innovations, for the purpose of illustrating theutilization of the present improvement, will serve to deflne the areasto which the technique is particularly applicable.

U.S. Pat. No. 3,560,587 (Cl. 260-683.48) describes the hydrogen fluoridealkylation of an isoparaffin/olefin mixture in a system whichincorporates a reaction cooler, reaction soaker and a hydrogen fluorideacidsettler. The greater proportion of the hydrogen fluoride phase,separated within the settler, is recycled to the cooled reaction zonefor further contact with the reactant mixture.

U.S. Pat. No. 3,686,354 (Cl. 260-683.43) is fairly illustrative of acomplete hydrogen fluoride alkylation system including reaction vessels,reaction effluent separation for acid recovery and product separationfor the recovery of the normally liquid alkylate product. In thissystem, the alkylate product is separated into a relatively high-octanefraction and a relatively lowoctane fraction, the latter being furthertreated with additional isoparaffin and hydrogen fluoride catalyst. U.S.Pat. No. 3,249,650 (Cl. 260-683.48) offers another fairly completeillustration of a hydrogen fluoride alkylation process in which aportion of the separated hydrogen fluoride is regenerated to recoverpolymer products; in this instance, the polymer products are utilized insupplying a portion of the required heat energy of the process.

The present control system is intended for utilization in I-IF-catalyzedalkylation processes of the type briefly described above. Theintegration and utilization of sophisticated control systems in apetroleum refining process is generally considered to be among recenttechnological innovations. In this respect, the published literature isslowly developing its own field of art. For example, U.S. Pat. No.3,759,820 (Cl. 208-64) discloses the systematized control of amulti-reaction zone process in response to two different qualitycharacteristics of the ultimately desired product. U.S. Pat. No.3,649,202 (Cl. 23/253-A) involves the control of reaction zone severityin response to the octane rating of the normally liquid producteffluent, and is primarily directed toward the well known catalyticreforming process. Other examples of controlling petroleum refiningprocesses are found in U.S. Pat. No. 3,751,229

(Cl. 23-253A), U.S. Pat. No. 3,748,448 (Cl. 235-l5l.l2) and U.S. Pat.No. 3,756,921 (Cl. 196.132).

As hereinbefore stated, the present control system is utilized toalleviate the problems attendant reaction zone temperature control in anacid-catalyzed alkylation process wherein an isoparaffin is alkylatedwith a mixed oleflnic feed stream. The difficulties arising out of theutilization of an oleflnic feed stream containing propylene, l-butene,Z-butene and isobutylene do not appear to be recognized either in theappropriate alkylation art, or in the control system publishedliterature.

SUMMARY OF INVENTION As hereinbefore set forth, my invention is directedtoward an improvement in the control of reaction zone temperature whilealkylating an isoparaffin/olefin reactant stream. Although particularlyapplicable to the alkylation of isobutane with a butylene-containingolefinic stream, the process is also adaptable for utilization withother isoparafflnic and olefinic feed stocks for the purpose ofproducing motor fuel or aviation alkylates. Suitable isoparaffmichydrocarbons are those having from about 4 to about 7 carbon atoms permolecule, including isobutane, isopentane, neopentane, one or more ofthe isohexanes and various branched-chain heptanes. Similarly theolefinic reactant contains from about three to about seven carbon atomsper molecule, and includes propylene, l-butene, Z-butene, isobutylene,the isomeric amylenes, hexenes, and various heptanes.

The alkylation reaction mixture comprises hydrogen fluoride catalyst, anisoparaffin and a mixed olefinic feed stream. With respect to thelatter, the feed stream generally contains at least two olefinichydrocarbons selected from the group consisting of propylene, lbutene,Z-butene and isobutylene. The hydrogen fluoride catalyst is utilized inan amount generally sufficient to provide a catalyst/hydrocarbon volumeratio, within the reaction zone, of from about 0.5 to about 3.0.Hydrogen fluoride, as utilized throughout the present specification andappended claims, is intended to include catalysts where hydrogenfluoride is the active ingredient. As a general practice, commercialanhydrous hydrogen fluoride will be charged to the alkylation system asfresh catalyst. It is possible to use hydrogen fluoride containing asmuch as about 10.0% water; however, excessive dilution with water'isundesirable since it tends to reduce the alkylating activity of thecatalyst and simultaneously introduces severe corrosion problems intothe system. In order to reduce the tendency of the olefinic portion ofthe hydrocarbon feedstock to undergo polymerization prior to alkylation,the molar proportion of the isoparaffin to olefinic hydrocarbons withinthe alkylation reaction zone is maintained at a value greater than about1.0: l .0, up to about 20.0210, and preferably from about 3.0:l.0 toabout 15011.0.

Alkylation reaction conditions include temperatures in the range ofabout 0 to about 200F., and preferably from about 30F. to about llOF. Inview of the fact that the alkylation reaction is highly exothermic,suitable means for removing heat from the reaction zone is generallyprovided. In general practice, the reaction zone is designed such thatit functions as a form of heat-exchanger. A cooling medium is introducedinto the reaction zone and indirectly contacts the reaction mixturetherein. The quantity of cooling medium is controlled by direct responseto the internal temperature. While such a basic technique admittedlyoffers some form of temperature control, it is clearly susceptible to arelatively large cycling range. In effect, this technique maintains thereaction zone temperature above a predetermined minimum and below thepredetermined maximum, the latter to avoid polymerization reactionswhich adversely affect ultimate'product quality.

Alkylation pressures are sufficiently high to maintain the hydrocarbonfeed stream and hydrogen fluoride catalyst in substantially liquidphase; that is, from about psig. to about 600 psig. The contact time inthe alkylation reaction zone is most conveniently expressed in terms ofa space-time relationship which is defined as the volume of catalystwithin the reactor or contacting zone, divided by the volume rate perminute of hydrocarbon reactants charged to the zone. Usually, thespace-time relationship will be less than about 5 minutes and preferablyless than about 2 minutes.

The product effluent from the alkylation reaction zone is introducedinto a separation zone generally comprising a two-vessel stacked system.The reaction mixture is introduced into the lower vessel which serves asa vertical mixer, or soaking zone. The mixer is sized and designed toprovide an average residence time in the range of about 60 seconds toabout 1200 seconds, depending upon the composition of the mixture beingcharged to the mixer-settler. After the desired residence time has beenattained, the effluent is introduced into the upper vessel which servesas a settler to provide a hydrocarbon stream substantially free from themajor portion of hydrogen fluoride, and settled hydrogen fluoridesubstantially free from the major proportion of hydrocarbons. Inaccordance with a relatively recent technique, at leasta portion of thereaction zone effluent is emulsified and recycled to the alkylationreaction zone. The settled hydrogen fluoride is recycled to the reactionzone in admixture with regenerated hydrogen fluoride. The reaction zoneeffluent generally contains a relatively minor proportion of polymerproducts formed during the alkylation reaction, notwithstandingtemperature control of the reaction mixture within the reaction zone. Inorder to prevent the buildup of polymer products within the system, arelatively minor proportion of the settled hydrogen fluoride phase,containing polymer products, is introduced into an acid regenerator.Recovered hydrogen fluoride is recycled to the alkylation reaction zonein admixture with the settled hydrogen fluoride.

The hydrocarbon phase separated in the settler vessel is introduced intoan isostripper fractionating column for therecovery of the normallyliquid alkylate product as a bottoms stream. Propane, unreactedisobutane and a minor quantity of hydrogen fluoride catalyst are removed as an overhead stream and introduced into a settling zone fromwhich the hydrogen fluoride is recycled to the reaction zone. Thehydrocarbon phase from this settler is introduced into a depropanizingcolumn with isobutane being removed as a bottoms fraction and recycledin part to the reaction zone and in part to the acid-regenerator for thepurpose of stripping hydrogen fluoride from the polymer products whichare removed as a bottoms phase. A principally vaporous phase,predominantly propane and containing a minor quantity of hydrogenfluoride is introduced into a hydrogen fluoride stripping column. Thehydrogen fluoride is removed as an overhead fraction and introduced intothe isostripper settler for ultimate return to the reaction zone.Propane is normally removed from the bottom of the hydrogen fluoridestripper and sent to storage. The propane-rich product stream isgenerally subjected to both alumina treating and potassium hydroxidetreating to remove trace quantities of hydrogen fluoride. Similarly,although the normally liquid alkylate product is generally recoveredsubstantially free from hydrogen fluoride, cautious operating techniquesgenerally dictate that the same be subjected to similar treatments toremove trace quantities of hydrogen fluoride.

The foregoing is representative of a typical, fairly complete hydrogenfluoride-catalyzed alkylation process. As previously stated, the presentinvention is intended for integration into such a unit for the purposeof achieving a greater degree of efficiency with respect to reactionzone temperature control accompanied by an enhancement of thesteady-state operation of the entire system. As a general rule, thecharacter of the olefinic feed stream to an HF alkylation unit isdependent upon the operation of other processes in the refinery. Sincethese other processes are subject to their own peculiar operatingparameters, the composition of the olefinic feed stream is constantlychanging. This contributes a particular problem with respect totemperature control of the alkylation reaction mixture. Considering onlypropylene, l-butene, 2-butene and isobutylene, the normally liquidalkylate product quality is improved by increasing the reactiontemperature, with respect to l-butene, and by decreasing the tem- 7perature of the reaction mixture with respect to 2- butene, orisobutylene. This difficulty is further compounded by virtue of the factthat a higher quality alkylate product results from a propylene feedstream processed at higher temperatures than those which are consideredoptimum for the alkylation of C -olefins.

In accordance with.the present invention, a hydrocarbon analyzer isutilized to receive a sample of the normally liquid alkylate product,preferably continuously, and to develop an output signal which isrepresentative of a composition characteristic of the sample. The outputsignal is transmitted by the hydrocarbon analyzer to signal-receivingmeans, or controller means, the latter in turn transmitting the signalto flowvarying means whereby the flow of the cooling medium into thealkylation reaction zone is adjusted in response to the varyingcomposition characteristic. In a preferred embodiment, the output signalis initially transmitted to comparator means which compares the rate ofchange and actual value of the composition characteristic, generates asecond output signal and transmits the same to the signal-receivingmeans.

Complete details of'the hydrocarbon analyzer, intended for utilizationas an essential element of the present control system, may be obtainedupon reference to U.S. Pat. No. 3,463,613 (Cl. 23-230). As statedtherein, a composition characteristic of a hydrocarbon sample can bedetermined by burning the same in a combustion tube under conditionswhich generate a stabilized cool flame. The position of the flame frontis automatically detected and employed to develop a signal which, inturn, is employed to vary a combustion parameter, such as combustionpressure, induction zone temperature or air flow, in a manner whichimmobilizes the flame front regardless of changes in the compositioncharacteristics of the hydrocarbon sample. The change in the combustionparameter, required to immobilize the flame following a change of samplecomposition, is corollatable with the composition characteristic change.An appropriate read-out device, connecting therewith, may be calibratedin terms of the desired identifying characteristic as, for example, theoctane rating.

The hydrocarbon analyzer is conveniently identified as comprising astabilized cool flame generator with a servo-positioned flame front. Thetype of analysis effected thereby is not a compound-by-compound analysissuch as presented by instruments including mass spectrometers, or vaporphase chromatographs. On the contrary, the analysis is represented by acontinuous output signal which is responsive to and indicative ofhydrocarbon composition and, more specifically, is corollatable with oneor more conventional identifications or specifications of petroleumproducts such as Reid vapor pressure, ASTM or Engler distillations, or,for motor fuels, anti-knock characteristics such as research octanenumber, motor octane number or a composite of such octane numbers.

The hydrocarbon analyzer used herein receives a hydrocarbon samplecontaining predominately gasoline boiling range components, and theoutput signal of which provides a direct measure of octane number. Forbrevity, the hydrocarbon analyzer is herein referred to as an octanemonitor.

As hereinbefore stated, the control system will further includecomparator means which receives the output signal from the hydrocarbonanalyzer, and compares the rate of change and actual value of thecomposition characteristic. A second output signal is generated andtransmitted to the signal-receiving means, or flow control means, toreset the set point thereof in response to successive comparisons of thecomposition characteristic. The flow control means in turn transmits thesignal to flow-varying means, whereby the flow of the cooling medium isadjusted in response thereto. Second comparator means can be-includedwithin the control system for comparing the actual value of thecomposition characteristic with previously determined deviation limitsand for generating an adjustment signal in response to this comparison.When the value lies beyond the limits, and the rate of change withrespect to time indicates that the value will continue to depart fromsuch limits, the second comparator means will generate an adjustmentsignal to alter the rate of change. Details of comparator means, asutilized in a control system for a reaction process, may be found inU.S. Pat. No. 3,748,448 (Cl. 235-15l.12).

In further describing my invention, reference will be made to theaccompanying drawing which is presented for the sole purpose ofdescribing a typical prior art HF alkylation process having integratedtherein the control system of the present invention. In the drawing, theprocess is presented by means of a simplified flow diagram in whichdetails such as pumps, instrumentation and other controls, quenchsystems, heat-exchange and heat-recovery circuits, valving, start-uplines and similar hardware have been eliminated as non-essential to anunderstanding of the techniques involved. The use of such miscellaneousappurtenances, to modify the process as illustrated, will be evident tothose possessing the requisite skill in the art of petroleum refiningtechnology.

DESCRIPTION OF DRAWING The drawing will be described in conjunction witha commercially-scaled unit designed for the alkylation of isobutane witha mixed olefin feed, containing propylene, butylenes and amylenes; in anexchangertype reaction vessel. The olefinic hydrocarbon stream, in theamount of about 7,126 BbL/day, enters the process via line 1; make-upisobutane is introduced via line 3; and, field butane, in the amount of1,200 BbL/day is introduced into the system via line 20, theisobutanerich portion thereof being recycled by way of line 2 to combinewith the olefinic hydrocarbon and make-up isobutane mixture in line 1.

From these fresh feed charge streams, it is desired to produce a fullboiling range, normally liquid alkylate product having a Reid vaporpressure of about 10.0 pounds and a clear (unleaded) octane rating ofabout 93.0; it is further intended to recover LPG grade (liquefiedpetroleum gas) propane, as well as a normal butane concentrate which istransported to storage.

With specific reference now to the drawing, 7,126 Bbl./day of theolefinic feed stream (1,149.79 moles/- hour), is introduced into theprocess through line 1, and is admixed with 64,841 Bbl./day (9,239.69moles/- hour) of an isobutane-rich recycle stream in line 2, containing139.31 moles of HF acid, and 3,188 Bbl./day (451.94 moles/hour) ofmake-up isobutane (95.0% by volume) from line 3, the mixture continuingthrough line 1 into alkylation reactor 4. The reactor is designed tofunction as a heat-exchanger having multiple feed injection points,which design is well known and not, therefore, illustrated herein,Hydrogen fluoride, in an amount of 1 14,868 Bbl./day (70,5318moles/hour), is recycled from settler 13 into reactor 4 by way of line5. This stream is inclusive of 220.94 moles/- hour of regenerated acidfromline 6, also containing 386.50 moles/hour of an isobutane-richstream, and 139.31 moles/hour of settled HF acid recovered in line 7 ashereinafter described. In reactor 4, the isobutane- /olefinichydrocarbon mole ratio is about 13.0210 and the HF acid/hydrocarbonvolumetric ratio is about 1.48: 1 .0. Reactor 4 is maintained at apressure of about 233 psig., with the HF acid and reactant streams beingintroduced at a temperature of about 100F. The mate rial balance aroundreaction zone 4, exclusive of the HF acid stream, is presented in thefollowing TABLE 1, with the concentrations of the various componentsbeing given in terms of moles per hour for convenience.

10 ator 15. For the purpose of simplifying the present illustration, itwill be presumed that the 221.16 moles/- hour of HF (inclusive ofpolymer products) continues through line 14 into regenerator 15.Regenerator 15 functions at a bottom pressure of about 155 psig., abottom temperature of about 350F., a top pressure of about 145 psig. anda top temperature of about 160F. HF acid is stripped from polymerproducts by the introduction, via line 16, of an isobutane-rich stream(275.88 moles/hour), at a temperature of 450F. and pressure of 160 psig.Polymer products, in the amount of 4.2 Bbl./day (0.22 moles/hour) arerecovered through line 17, at a pressure of about 155 psig. and atemperature of about 350F. A portion of the isobutane-rich stream fromline 16 is diverted through line 32 in the amount of 110.62 moles/hour,cooled to a TABLE temperature of about 100F., and introduced as refluxinto acid regenerator 15. The overhead stream in line C t Ream" afBalance Em t 6, comprising 386.50 moles/hour of hydrocarbons and omponenarge mm 220.94 moles/hour of regenerated HF acid, is recycled Ethane 120to combine with the settled acid in line 5, and returned Propylene352.94 propane 75355 77962 to reactor 4. The material balance withrespect to acid Butylenes 333-12 regenerator 15 is presented in thefollowing TABLE II: lsobutane 8965.48 8258.10 N-Butane 657.30 663.47

TABLE ll:

Acid Regenerator Material Balance Component Line Number Ethane PropylenePropane 1.30 8.40 9.70 Butylenes lsobutane 102.26 258.47 360.73 N-Butane6.38 8.39 14.77 Amylenes lsopentane 0.67 0.62 1.29 N-Pentane Hexane-plusHF Acid 220.94 220.94 Polymers 0.22 0.22

Amylenes 3.59 The hydrocarbon-rich phase from .settler 13, at alsopenmne 104-59 128-54 temperature of about 100F. and a pressure ofabout N-Pentane 0.77 203 h h 18 d f Hexane p|us 4920 7O4 |2 psig. 1Swithdrawn t roug me an consists o Polymer Products 0.22 10,535.05moles/hour of hydrocarbons and 276.62

As hereinbefore set forth, HF alkylation of an isoparaffin/olefinreactant mixture is highly exothermic, and must be tempered through theuse of a cooling medium. In the illustration, the exothermic heat ofreaction is removed through the use of 10,422 gallons/minute of water(about 85F.) entering via line 9, and exiting via line 8 at atemperature of about 90F. The total reaction product effluent iswithdrawn through line 10 at a temperature of about 100F. and a pressureof about 218 psig.

The product effluent continues through line 10 into mixer/soaker 11,wherein it is maintained for an effective residence time of about 8minutes. After this holding period, the product effluent is transferredvia line 12 into HF acid settler 13. Settled HF acid is removed via line14 in the amount of 114,415 Bbl./day (70,252.80 moles/hour), at apressure of about 203 psig. Of this amount, 1 14,055 Bbl./day (70,032moles/- hour) are diverted through line 5 as acid recycle to reactor 4.Generally, the remaining 360 Bbl./day (221.16 moles/hour) is accumulateduntil a sufficient quantity is available for introduction intoacidregenermoles/hour of HF acid. This material is heated to a temperatureof about 170F., and introduced into isostripper 19 at a pressure ofabout 152 psig. Field butane, at a temperature of about F., enters theupper section of isostripper 19 through line 20, in an amount of 172.99moles/hour. A normal butane-rich stream, in the amount of 115.91moles/hour, is recovered as a side-cut via line 21, and is subjected totreatment with potassium hydroxide for the removal of trace quantitiesof HF acid. lsostripper 19 functions at a bottom temperature of about371F., a bottom pressure of about 160 psig., a top temperature of aboutF. and a top pressure of about 152 psig. The normally liquid alkylateproduct is recovered through line 22 in an amount of 7,711 BbL/day(753.96 moles/hour), and is also subjected to caustic treating for acidremoval. An isobutane-rich stream, in the amount of 8,966.66 moles/hour,including 25.54 moles/hour of a pump flush stream (not illustrated) fromdepropanizer 27 is recycled via lines 2 and 1 to reactor 4. Alsorecovered in line 2 is HF acid in the amount of 139.31 moles/hour.Overhead vapors, consisting of 1,794.10 moles/hour of hydrocarbons and157.10 moles/hour of HF acid, is withdrawn through line 23. Of thisamount, 897.05

moles/hour of hydrocarbons and 17.80 moles/hour of HF are used as refluxto isostripper 19; the composition of the hydrocarbon phase is 1.18moles of ethane, 216.52 moles of propane, 643.80 moles of isobutane,32.39 moles of n-butane and 3.17 moles of isopentane. The componentcomposition of the various charge and effluent streams, exclusive of HFacid, are presented in the following TABLES 111 and 1V:

TABLE III isostripper Feed Streams Component Line 18 Line 20 Ethane 1.20

Propylene Propane 779.62 4.03 Butylenes lsobutane 8258.10 81.42 N-Butane662.63 84.49 Amylenes lsopentane 128.54 1.97 N-Pentane 1 .08 Hexane-plus704.12

TABLE IV lsostripper Effluent Streams Component Line 23 Line 2 Line 21Line 22 Ethane 2.38

Propylene Propane 436.94 536.52 Butylenes lsobutane 1284.08 7715.72 5.591.52 N-Butane 64.40 543.85 108.26 65 30 Amylenes lsopentane 6.29 94.371.97 31.21 N-Pentanc 0.90 Hexane-plus 49.20 0.08 654.84

A portion of the overhead from line 23 is diverted as reflux to the topof the isostripper 19; this portion consists of 897.05 moles/hour ofhydrocarbons and 17.80 moles/hour of HF. The remainder is admixed with18.26 moles/hour of HF from line 24, and is introduced into settler 25.

Settled acid, in the amount of 139.31 moles/hour, is recycled to reactor4 by way of lines 7 and 5. Hydrocarbons. in the amount of 914.04moles/hour, and HF acid, in the amount of 18.26 moles/hour, areintroduced via line 26 into depropanizer 27. A propane concentratecontaining 18.26 moles/hour of HF acid is recovered as'an overheadstream in line 28, being introduced thereby into HF stripper 29. Thebottoms stream, 702.04 moles/hour is withdrawn through line 30 andutilized as follows: 42.56 moles/hour are employed as a pump flushstream (not illustrated); 386.50 moles/hour are diverted through line 16for use in acid regenerator l; and, 273.02 moles/hour continue throughline 30 for recycle to reactor 4 via line 2. Depropanizer 27 functionswith a bottom pressure of about 3.5 psig., a bottom temperature of about220F., a top temperature of about 140F. and a top pressure of about 305psig. The material balance for depropanizer 27 is presented in thefollowing TABLE V:

TABLE V-continued lsopentane 3 .23 3.23

Hydrogen fluoride, in an amount of about 18.26 moles/hour is withdrawnas an overhead stream in line 24, and admixed with the isostripperoverhead in line 23. The 21 1.99 moles/hour of hydrocarbons arerecovered via line 31. HF stripper 29 functions with a top temperatureof about 140F., and a pressure of about 310 psig. and a bottomstemperature of 150F., and a pressure of about 320 psig.

The normally liquid alkylate product withdrawn via line 22 has a ReidVapor Pressure of 9.9 lbs., a clear octane rating of 93.3 (researchmethod), 104.2 with 3.0 cc. of tetraethyl lead, and a gravity of 74.6AP1. The results of a 100-ml. ASTM distillation are presented in thefollowing TABLE VI:

TABLE VI Alkylate Product ASTM Distillation Volume Percent Octanemonitor 41 is field-installed adjacent isostripper 19; it utilizes astabilized cool flame generator having a servo-positioned flame front.The flow of oxidizer (air) and fuel (alkylate product effluent from line22) are fixed, as is the induction zone temperature. Combustion pressureis the parameter which is varied in such a manner that the stabilizedcool flame front is immobilized. Upon experiencing and detecting achange in a composition characteristic, in this illustration octanenumber, the change in pressure required to immobilize the flame frontwithin the octane monitor provides a direct indication of the change inthe sample delivered to the analyzers combustion chamber by way of line33. Typical operating conditions for the octane monitor are: air flow,3,500 cc./min. (STP); fuel flow, 1.0 cc./min.; induction zonetemperatures, Research Octane, 700F.; induction zone temperature, MotorOctane, 800F.; combustion pressure, 4.0 to 20.0 psig.; and, octane range(max), to 102.

The actual calibrated span of the octane monitor as herein employed,will generally be considerably narrower. For example, where the targetoctane rating is 95.0 Clear (Research Method), a suitable span may be-96 research octane. When such a relatively narrow span is employed, theoctane number change is essentially directly proportional to the changein combustion pressure. As shown in the drawing, the sample system maycomprise a sample loop taking, for example, liquid at a rate of cc./min.via line 33 and returning it by way ofline 34, the sample itself beinginjected, from an 13 intermediate point at a controlled rate, by ametering pump to the combustion tube of the octane monitor.

The octane monitor output signal is transmitted through line 35 toultimately reset the set point of controller 38. The latter will thenmake the appropriate adjustment, by way of line 39, in control valve 40,either to decrease, or increase the flow rate of the cooling medium inline 9. It is understood, of course, that control valve 40 can beinstalled in line 8, the cooling medium exit line from reaction zone 4.In a preferred technique, the octane monitor output signal istransmitted via line 35 into comparator means 36, and therefrom throughline 37 into controller 38. Since the sample of alkylate product fromline 22 is taken continuously, and a varying output signal iscontinuously transmitted via line 35, rapid compensation for the changein olefinic composition of the feed stream in line 1 is afforded.

To illustrate further, it will be presumed that an initial change infeed stream composition constitutes an increase in the content ofl-butene. Therefore, the temperature of the reaction mixture in reactor4 is too low and must be increased. Octane monitor 41 senses thedecreasing octane number and transmits an output signal through line 35to comparator 36. The latter compares and checks the current signalagainst the previous signal and transmits an output signal to controller38, via line 37, in order to correct the difference and reset its setpoint. Controller 38 transmits a signal, via line 39, such that controlvalve 40 is caused to close to decrease the flow of cooling medium andthus increase the reaction temperature. As will be recognized,comparator 36 is extremely advantageous where a second feed streamcomposition change i.e. a decrease in isobutylene content follows soonafter the first.

Through the utilization of the present control system, a refineryfunctioning with a mixed olefin feed stream, as the charge to an HFalkylation system, is afforded close control over either a desiredtarget octane rating, or over maximizing the octane rating, regardlessof the changes in feed composition.

I claim as my invention:

l. A process for alkylating an isoparaffin with an olefinic feed streamcontaining at least two olefins, which process comprises the steps of:

a. reacting said isoparaffin with said feed stream in admixture with ahydrogen fluoride catalyst, in an alkylation reaction zone, atalkylating conditions resulting in a reaction product effluentcontaining normally liquid alkylate;

. regulating the temperature of the reaction mixture, within saidreaction zone, through indirect contact of said reaction mixture with acooling medium passing through conduit means through said reaction zone,the flow of said cooling medium being adjusted by flow-varying meansconnected to said conduit means;

. recovering said normally liquid alkylate from said product effluent;

. introducing a sample of said alkylate into a hydrocarbon analyzer anddeveloping therein an output signal which is representative of acomposition characteristic of said sample; and,

. transmitting said output signal to signal-receiving means and fromsaid signal-receiving means to said flow-varying means, whereby the flowof cooling medium through said conduit means and the temperature withinsaid reaction zone is adjusted in response to said compositioncharacteristic.

2. The process of claim 1 further characterized in that said olefmicfeed stream contains at least two olefins having from 3 to 7 carbonatoms per molecule.

3. The process of claim 1 further characterized in that said isoparaffincontains from 4 to 7 carbon atoms per molecule.

4. The process of claim 2 further characterized in that said olefinicfeed stream contains at least two olefins selected from the groupconsisting of propylene, l-butene, 2-butene, and isobutylene.

5. The process of claim 3 further characterized in that said isoparaffinis isobutane.

6. The process of claim 1 further characterized in that said alkylatingconditions include an isoparaffinlolefin molar ratio in the range ofabout l.l:l.0 to about 20.0:l.0 and a reaction zone temperature fromabout 30F. to about 200F.

1. A PROCESS FOR ALKYLATING AN ISOPARAFFIN WITH AN OLEFINIC FEED STREAMCONTAINING AT LEAST TWO OLEFINS, WHICH PROCESS COMPRISES THE STEPS OF:A. REACTING SAID ISOPARAFFIN WITH SAID FEED STREAM IN ADMIXTURE WITH AHYDROGEN FLUORIDE CATALYST, IN AN ALKYLATION REACTION ZONE, ATALKYLATING CONDITIONS RESULTING IN A REACTION PRODUCT EFFLUENTCONTAINING NORMALLY LIQUID ALKYLATE; B. REGULATING THE TEMPERATURE OFTHE REACTION MIXTURE, WITHIN SAID REACTION ZONE, THROUGH INDIRECTCONTACT OF SAID REACTION MIXTURE WITH A COOLING MEDIUM PASSING THROUGHCONDUIT MEANS THROUGH SAID REACTION ZONE, THE FLOW OF SAID COOLINGMEDIUM BEING ADJUSTED BY FLOW-VARYING MEANS CONNECTED TO SAID CONDUITMEANS; C. RECOVERING SAID NORMALLY LIQUID ALKYLATE FROM SAID PRODUCTEFFLUENT; D. INTRODUCING A SAMPLE OF SAID ALKYLATE INTO A HYDROCARBONANALYZER AND DEVELOPING THEREIN AN OUTPUT SIGNAL WHICH IS REPRESENTATIVEOF A COMPOSITION CHARACTERISTIC OF SAID SAMPLE; AND E. TRANSMITTING SAIDOUTPUT SIGNAL TO SIGNAL-RECEIVING MEANS AND FROM SAID SIGNAL-RECEIVINGMEANS TO SAID FLOW-VARYING MEANS, WHEREBY THE FLOW OF COOLING MEDIUMTHROUGH SAID CONDUIT MEANS AND THE TEMPERATURE WITHIN SAID REACTION ZONEIS ADJUSTED IN RESPONSE TO SAID COMPOSITION CHARACTERISTIC.
 2. Theprocess of claim 1 further characterized in that said olefinic feedstream contains at least two olefins having from 3 to 7 carbon atoms permolecule.
 3. The process of claim 1 further characterized in that saidisoparaffin contains from 4 to 7 carbon atoms per molecule.
 4. Theprocess of claim 2 further characterized in that said olefinic feedstream contains at least two olefins selected from the group consistingof propylene, 1-butene, 2-butene, and isobutylene.
 5. The process ofclaim 3 further characterized in that said isoparaffin is isobutane. 6.The process of claim 1 further characterized in that said alkylatingconditions include an isoparaffin/olefin molar ratio in the range ofabout 1.1:1.0 to about 20.0:1.0 and a reaction zone temperature fromabout 30*F. to about 200*F.